The bill, unanimously adopted by France's upper house, the Senate, on Thursday, means that anyone holding people against their will and making them work for free, will face between seven and 30 years in prison.
Romana Cacholi, head of advocacy with London-based Anti-Slavery International, told RFI that his organisation welcomes France's tough stance.
Almost 21 milllion people around the world are currently victims of forced labour, according to the International Labour Organisation.
French anti-slavery campaigners receive more than 200 reports of enslavement per year but believe that it is much more widespread, because it happens in private, often within families.
"They hope to find a better life in France," she explained. "They are vulnerable and most of the time, have no clue about our country or our laws. They are therefore easy prey for unscrupulous people."
The group will now be helping to train the police and legal teams to identify victims of slavery.